Silicon carbide, as an artificially synthesized carbide, finds extensive applications in industries, particularly in the abrasives sector. The reason why silicon carbide is frequently used as an abrasive lies in its inherent chemical and physical properties. In this article, we are about to delve into the topic of silicon carbide hardness.
1.1 Chemical Composition and Crystal Structure
Silicon Carbide Silicon carbide (SiC) is a compound composed of silicon (Si) and carbon (C) elements. Its chemical formula is SiC, and generally, silicon carbide is formed by the combination of carbon and silicon in a 1:1 ratio. Pure silicon carbide is typically a transparent crystal; however, in industrial applications, impurities in silicon carbide may lead to variations in color, such as common black silicon carbide and green silicon carbide. Silicon carbide often exhibits various crystal structures, with the most common being cubic crystal structure (β-SiC) and hexagonal crystal structure (α-SiC). At temperatures above 2100°C, β-SiC transitions to the α-SiC structure. Currently, more than 70 different forms of α-SiC have been identified. The preparation methods for silicon carbide vary.
2.1 Definition and Measurement
Hardness is the ability of a material to resist scratching, piercing, or indentation, commonly indicating the material’s resistance to abrasion and wear. The hardness measurement methods for silicon carbide include the following four:
Mohs Hardness: The Mohs hardness of silicon carbide is typically between 9-9.5.
Mohs hardness for black silicon carbide: 9.2-9.3
Mohs hardness for green silicon carbide: 9.4-9.5
Vickers Hardness: The Vickers hardness of silicon carbide usually ranges between 2800-3400 HV.
Vickers hardness range for black silicon carbide: 2800-3200 HV
Vickers hardness range for green silicon carbide: 3100-3400 HV
The Vickers hardness test involves applying a specific load to the material’s surface and measuring the diagonal length of the resulting indentation, from which the Vickers hardness value can be calculated.
Brinell Hardness: The Brinell hardness is determined by applying a certain load to the material’s surface and then measuring the diameter of the resulting indentation. Generally, the Brinell hardness range for silicon carbide is 2400-2800 HBS.
Brinell hardness range for black silicon carbide: 2400-2600 HBS
Brinell hardness range for green silicon carbide: 2600-2800 HBS
Rockwell Hardness: The Rockwell hardness is determined by applying static or dynamic loads to the material’s surface and measuring the depth of the hardness gauge. Generally,
Rockwell hardness range for black silicon carbide: 83-87 HRA
Rockwell hardness range for green silicon carbide: 87-92 HRA
Hardness Testing Methods
Test Value Range
Specific Values (Black Silicon Carbide)
Specific Values (Green Silicon Carbide)
2.2Factors Affecting Silicon Carbide Hardness
Crystal Structure: As analyzed earlier, the crystal structure of silicon carbide plays a significant role. The hexagonal crystal structure of silicon carbide (α-SiC) generally exhibits higher hardness compared to the cubic crystal structure (β-SiC). The tighter arrangement of atoms in the crystal structure leads to stronger bonding.
Purity: Purity is the second major factor influencing silicon carbide hardness. A lower presence of impurities indicates higher purity, correlating with increased hardness in silicon carbide.
Sintering Degree: The sintering degree represents the extent of heating during the manufacturing process of silicon carbide. Higher sintering degrees result in increased hardness because elevated temperatures lead to grain growth and higher material density.
Grain Size: Smaller grain sizes contribute to greater hardness in silicon carbide. This is attributed to the fact that grain boundaries are weaknesses in the material, and smaller grains imply fewer grain boundaries.
Based on the factors influencing silicon carbide hardness, we can artificially enhance the hardness of silicon carbide through various methods. Common approaches include doping, alloying, surface treatments, and other techniques.
3.1 Doping and Alloying for Hardness Enhancement
Silicon carbide can undergo changes in its electrical properties and improved mechanical performance through doping and alloying. Common methods include solid solution doping, ion implantation, chemical vapor deposition, powder metallurgy, followed by compaction and sintering. Through these processes, the hardness, strength, toughness, and wear resistance of silicon carbide can be significantly improved.
3.2 Surface Treatment
Surface treatment of silicon carbide is another approach to enhance its hardness. Techniques such as coating and plating can be employed to increase surface hardness, reduce wear, and improve lubrication.
Thermal Spray: Melting materials are sprayed onto the surface to form a coating. Common materials include ceramics, metals, and polymers.
Cold Spray: Solid material particles are accelerated to high speeds and then sprayed onto the silicon carbide surface. Common materials include metals and polymers.
Physical Vapor Deposition (PVD): A thin film is deposited on the silicon carbide surface. Common materials include metals, ceramics, and nitrides.
Chemical Vapor Deposition (CVD): A thin film is deposited on the silicon carbide surface. Common materials include ceramics and carbides.
3.3 Practical Applications of Enhanced Silicon Carbide Hardness
Selecting appropriate technologies and materials to meet specific application requirements is crucial. Enhanced silicon carbide hardness finds practical applications in various fields, such as SiC:N ceramic cutting tools, SiC ceramic aerospace components, SiC ceramic electronic device packaging materials, SiC ceramic artificial joints, and more. Improving silicon carbide hardness expands its application range and enhances its value in various industries.
As experts in the abrasives industry with 19 years of experience, Yafeite can provide you with optimal industry solutions and high-quality products. If you need silicon carbide and other abrasive products, please contact us:
How is the hardness of silicon carbide defined?
Answer: Hardness is the ability of a material to resist scratching, piercing, or indentation, typically indicating the material’s resistance to abrasion and wear. The hardness of silicon carbide can be measured using Mohs hardness, Vickers hardness, Brinell hardness, and Rockwell hardness, with Mohs hardness typically ranging between 9-9.5.
How does the crystal structure of silicon carbide affect its hardness?
Answer: Silicon carbide has various crystal structures, including cubic crystal structure (β-SiC) and hexagonal crystal structure (α-SiC). Generally, hexagonal silicon carbide exhibits higher hardness than cubic silicon carbide due to its tighter crystal structure and stronger atomic bonding.
How is the hardness of silicon carbide measured?
Answer: The hardness of silicon carbide can be measured using Mohs hardness, Vickers hardness, Brinell hardness, and Rockwell hardness. These methods involve applying a load to the material’s surface and measuring the resulting indentation or hardness value to assess hardness.
What factors influence the hardness of silicon carbide?
Answer: Factors influencing silicon carbide hardness include crystal structure (higher hardness for hexagonal structure), purity (higher purity leads to higher hardness), sintering degree (higher sintering degree results in higher hardness), and grain size (smaller grains contribute to higher hardness).
How can the hardness of silicon carbide be enhanced?
Answer: The hardness of silicon carbide can be enhanced through methods such as doping, alloying, and surface treatment. Doping and alloying methods include solid solution doping, ion implantation, while surface treatment methods include coating and plating to increase surface hardness, reduce wear, and improve lubrication.